An example of an electron beam exposure apparatus includes, e.g., a point beam type apparatus which uses an electron beam formed into a spot, a variable shaped beam type apparatus which uses an electron beam formed into a variable-size rectangle, and a stencil mask type apparatus with which a stencil mask having a beam passing hole with a desired shape is formed in advance and which uses a beam formed into a desired shape with the stencil.
Although the point beam type apparatus is suitable for forming a micropattern, it is used only for research and development as its throughput is very low. The variable shaped beam type apparatus has a throughput higher than that of the point beam type apparatus by one or two orders of magnitude. This throughput, however, is still low to draw a pattern in which micropatterns of about 100 nm are packed at a high integration degree.
An example of a method that draw any pattern includes an exposure method using a two-dimensional blanking aperture array (e.g., see Japanese Utility Model Publication No. 56-19402). According to this method, a plurality of apertures for passing beams through them are two-dimensionally arranged in a large number in a semiconductor crystal substrate made of silicon or the like. A pair of blanking electrodes are formed on the two ends of each aperture, and whether to apply a voltage across the electrodes is controlled in accordance with pattern data. In other words, according to this method, whether to cause the plurality of beams respectively passing through the plurality of apertures to travel linearly or to deflect them is controlled individually, thereby individually controlling whether the plurality of beams are to irradiate a sample. For example, when one of the electrodes on the two ends of each aperture is grounded and a voltage is applied to the other electrode, the beam passing through this aperture is deflected. This beam is shielded by an aperture stop set under the blanking aperture array and does not irradiate the sample. If the voltage is not applied to the other electrode, the electron beam passing through the aperture is not deflected. Thus, the beam is not shielded by the aperture stop set under the blanking aperture array, and irradiates the sample surface.
FIG. 9 schematically shows the arrangement of the two-dimensional blanking aperture array. In the two-dimensional blanking aperture array, a plurality of apertures (AP) are two-dimensionally arranged, and each aperture has a pair of electrodes (EL). The two-dimensional blanking array aperture has wiring lines and elements for individually controlling voltages to be applied to the electrodes of the plurality of apertures in accordance with pattern data. For example, the apertures (AP) have diameters of 20 μm and are arranged with pitches of 100 μm. Each electrode (EL) has a thickness of 10 μm, a width of 10 μm, and a length (in the direction of the depth) of about 50 μm.
In general, when the surface of a sample is scanned with an electron beam to draw a pattern with a line width of 100 nm, the spot size of the electron beam on the spot must be 25 nm or less.
Currently, however, the sizes of the apertures of the blanker array are limited to 10 μm×10 μm at minimum due to limitations in the manufacture. To reduce the spot size of the electron beam, the shape of which is defined by such an aperture, with a reduction electron optical system to 25 nm or less, the reduction electron optical system must have a reduction magnification of 400 times, which is actually difficult to achieve.